In the manufacture of articles having internal cavities it is often necessary to determine whether or not the dimensions of the cavities are within prescribed limits for the production of satisfactory articles. One type of such article is an electrical connector having a channel-like opening into which extends two sets of contact portions of externally projecting terminals. These connectors are assembled with the channel-like opening functioning as a socket to receive a section of a printed circuit board having contact elements formed on the upper and lower surfaces along one edge thereof. If the connector is bowed so that the socket opening varies in wall spacings beyond certain limits, the individual terminal contact portions will not, or only weakly, engage the contact elements formed on the circuit board thus disrupting the integrity of any circuit continuity between the electrical components on the circuit board and the electrical equipment wired to the projecting terminals.